mpg drop after getting transmission fixed?

[davemsc]

Hey all,

Have a 2013 mazda 3 sky activ 6 speed with just under 100,000km. Had trouble with 3rd gear so they performed a TSB (I don't have it with me, but something like 05-12-06 - the one for hard shifting).
Anyway, my gas mileage seems to have really dropped.

Does this make sense? It seems to be shifting fine (the problem with 3rd gear is now gone), the RPMS seems right, but around town, the gas mileage is brutal.

Any idea why this might be?

Thanks,
dave

[morganc]

If this TSB involved a reflash of the ECU, then they could have changed fuel map settings. Since you're likely doing a lot of your driving in 3rd gear around town, this is likely the culprit.

[davemsc]

If this TSB involved a reflash of the ECU, then they could have changed fuel map settings. Since you're likely doing a lot of your driving in 3rd gear around town, this is likely the culprit.

Hey thanks for the response. So what does that mean exactly? Can they fix it or aM i stuck with it? Will it get better overtime?

[morganc]

Give the computer a week or two to learn the new fuel trim settings, but you're more thank likely stuck like this. There's really nothing they can 'fix', the ECU flash comes from corporate engineering and isn't configurable.

[davemsc]

Give the computer a week or two to learn the new fuel trim settings, but you're more thank likely stuck like this. There's really nothing they can 'fix', the ECU flash comes from corporate engineering and isn't configurable.

Really?? Wouldn't after a week it goes back to normal? I getting worse gas mileage now than when it was the dead of winter with snow tires on. The highway mileagae seems about the same (I can get about 130km before the first gas notch goes away if all highway at going 110km/hr on cruise). But the city is bad.

[morganc]

Well, again, it's never going to go back to 'normal'. This is your new normal. When fuel map setting are changed, there's only a tiny bit of room for automatic trim adjustment. I imagine that they had the engine running lean, which is why your economy was better, and the new ECU flash probably richens it.